Power supply systems are pervasive in many electronic applications from computers to automobiles. Generally, voltages within a power supply system are generated by performing a DC-DC, DC-AC, and/or AC-DC conversion by operating a switch loaded with an inductor or transformer. One class of such systems includes switched mode power supplies (SMPS). An SMPS is usually more efficient than other types of power conversion systems because power conversion is performed by controlled charging and discharging of the inductor or transformer and reduces energy lost due to power dissipation caused by resistive voltage drops.
One specific application of an SMPS is the conversion of an AC line voltage to a DC voltage. An example of such a system includes number of stages including a rectifying stage, a power factor converter (PFC) and a DC-DC converter. The rectifying stage, which may be implemented using a diode bridge, converts the AC line voltage into a unipolar rectified signal. The PFC produces intermediate DC voltage from the unipolar rectified signal, and the DC-DC converter produces a second DC output voltage, for example 12 V. The power factor converter may be further configured to ensure that the input current of the SMPS is in phase with the input voltage in order to minimize reactive power.